Process of refining hydrocarbon oils



Patented May 11, 1943 PROCESS OF REFDVINSG HYDROCARBON OIL Carl William Berger, McPherson, Kans assignor to Globe Oil and Refining Company, Wichita, Kans, a corporation of Kansas No Drawing. Application January 28, 1942, Serial No. 428,504

13 Claims.

This invention relates to a process of refining hydrocarbon oils and more particularly to a process of refining lighter gravity hydrocarbon oils produced in petroleum distillation and cracking processes for the purpose of removing or converting objectional mercaptans and other odorous and sulfur-bearing compounds.

In accordance with the prior art, mercaptans and other sulfur-bearing compounds have been removed to some extent from hydrocarbon oils by contacting the oils with aqueous alkaline solutions of potassium or sodium hydroxide. The success of these prior art refining processes apparently depends upon the solubility of the sodium or potassium mercaptides formed in the alkaline treating agent. However, in most cases these prior art processes fail to remove all of the cercaptans or even suificient of them to produce an oil which is sweet to the well known doctor test. The failure to accomplish a complete removal of these mercaptans appears to be due to the fact that different petroleum mercaptans vary in their solubilities in the alkaline solution. Prior investigators have sought successfully to increase the solubility of the alkali metal mercaptides in the alkaline treating agent through the addition of certain organic acids or salts, such as isobutyric acid or potassium isobutyrate. These solutizers are themselves largely unchanged through cycles of contact and regeneration of the alkaline treating agent and the results obtained when they are used are not always satisfactory. The present invention depends upon an entirely different method for the elimination of the mercaptan from the hydrocarbon oil. In accordance with my invention a substance is dissolved in an alkaline solution which enters directly into the refining reaction itself with the formation of complex salts, thereby removing the mercaptans and other odorous or sulfur-bearing compounds from the petroleum oils, or rendering them innocuous as to odor and reactability to sodium plumbite or other agents which normally show reaction with mercaptans. The final result of my process is that the petroleum oil is rendered sweet to the doctor test. The method may be conveniently used for sweetening and otherwise improving the lighter gravity liquid products produced in petroleum distillation and cracking, natural gasoline condensed from oil well vapors, or other liquids containing mercaptans and other odorous and sulfur-bearing compounds as impurities. In accordance with this invention, a hydrocarbon oil may be refined to remove or convert mercaptans and other odorous and sulfur-bearing compounds by contacting the oil with a refining agent comprising an alkaline solution of a compound selected from the group consisting of phosphorous pentasulfide and an alkali metal salt of a thio acid of phosphorus. The refining agent may be used alone or in combination with any other suitable refiningagent or agents to remove or convert the objectionable compounds which may be contained in the hydrocarbon oil to be refined.

I have discovered that when hydrocarbon oils and more particularly the lighter gravity liquid products produced in petroleum distillation and cracking processes are subjected to the action of the refining agent of this invention, certain reactions take place which do not occur when the phosphorous pentasulfide or the salt of a thio acid of phosphorus is not present in the alkaline solution. These reactions result in the improvement of the hydrocarbon oil which is treated. One of the important reactions that I have discovered as taking place when the hydrocarbon oil is treated with the refining agent in accordance with this invention is that the mercaptan content of the hydrocarbon liquid is materially decreased and in many cases the mercaptans may be completely, eliminated from the hydrocarbon oil.

In accordance with one preferred embodiment of this invention, an alkaline aqueous solution of phosphorous pentasulfide may be employed to effect the desired refining. Also the refining agent may comprise an aqueous alkaline solution of trisodium dithiop'hosphate', trisodium trithiophosphate, or the analogous salts of potassium.

In order to more specifically point out the nature of my present invention, an example of the manner in which it may be carried out is presented in the following. It will be understood, of course, that I do not wish to be limited, to the specific process disclosed since many modifications may be made as will be apparent to one skilled in the art.

In accordance with one embodiment of this invention, a phosphorous pentasulfide-alkali solution may beprepared b dissolving about Sperccnt by weight; of, phosphorous pentauslfide in an aqueous alkali solution of approximately 20 B. gravity containing approximately 16 percent of sodium hydroxide orpotassium hydroxide or both. The phosphorous pentasulfide may be dissolved inthe alkaline solution at room temperature whi-lebeingstirred, but,;if-desired, the solution may beheated gently in order to effect a ever, any concentration of the phosphorous pentasulfide or the alkali in the solution may be effective. Preferably the alkaline solution should contain more than about one-half of one per-' cent by weight of the phosphorou pentasulfide.

The solution prepared in the manner indicated above will sweeten any gasoline which I have thus once for a period of 5 minutes with the B. caustic solution containing 3.0 percent by weight of phosphorous pentasulfide. Upon examination of this once-treated gasoline it was found to be completely sweet and free of mercaptan sulfur.

In each case where sour gasoline was sweetened by my process. the color, theodor, and the corrosion test of the gasoline was greatly improved.

'I'have also sweetened both cracked and straightrun gasolines by this method which contained more than ten times the mercaptan sulfur content of the gasoline described in the foregoing far treated by my method, including cracked gasoline of full distillation range and straight-run gasoline of full distillation range. The gasoline is contacted with the treating agent in the liquid phase by vigorous agitation for a period .ofonehalf minute to 20 minutes, depending upon the type of petroleum oil or the type of mercaptans contained therein. The volume ratio between the hydrocarbon liquid to be refined and the treating agent have been successful in ranges from one part of treating solution per 100 parts of hydrocarbon oil to an infinite amount of treating solution as compared with the volume of the hydrocarbon oil.

In order to demonstrate the fact that very much improved results are obtained when'phosphorous pentasulfide or the salt of a thio acid of phosphorus are contained in the alkaline solution, various experiments have been conducted. The following experiment is typical and clearly shows the desirable results that are obtained by my new process. A blended sour gasoline con- .taining 0.007 percent by weight of mercaptan sulfur was contacted for 5 minutes at 80 F. with an equal volume of 20 B. aqueous caustic solution. A small portion of this treated gasoline was ..tested and found to be sour and to contain 0.004

percent by weight of mercaptan sulfur; The balance of the gasoline was again shaken with a .fresh solution of 20 B. caustic solution under the same conditions for another 5 minutes and another small portion was tested, the results showing that the twice-treated gasoline was still sour but now contained 0.0035 percent of mercaptan sulfur by weight. The same gasoline was for a third time shaken with fresh caustic solution the mercaptan sulfur was removed. This thricecaustic-washed gasoline was then shaken with a 20 B. caustic soda solution having dissolved therein 3 percent by weight of phosphorous pentasulfide for a period of 5 minutes, this alkaline pentasulfide solution having been prepared in the manner indicated above. It was found that this single treatment of the previously causticwashed gasoline completely sweetened the gasoline and it was found to be entirely free of mercaptan sulfur. Thus it is clear that the phosphorous pentasulfide dissolved in the caustic soda solution exhibited a purifying effect which was not obtainable by the use of the caustic solution alone.

As further evidence of the: efiicacy of my process, an originally sour gasoline containing 0.007

percent of mercaptan sulfur by weight was shaken experiments. Heavier oils, such as naphthas, kerosenes and distillates, may also be improved by the process. In some cases, when these heavier products are refined, more than one treatment may be necessary. As has been indicated in the "foregoing, I prefer to use for my treating agent phosphorous pentasulfide dissolved in an aqueous solution of sodium or potassium hydroxide. However, other alkaline solutions may be employed if desired. Likewise for the phosphorous pentasulfide I may substitute certain salts of the thio acids of phosphorus, such as trisodium dithiophosphate, trisodium trithiophosphate or the potassium salts of said thiophosphates. I have found that under certain conditions the potassium salts are more reactive than the salts of sodium. Also any proportions of ingredients in the refining agent may be employed which will effect the desired results.

Any suitable method may be employed for contacting the refining agent with the hydrocarbon oil in accordance with the processes of this invention. The requirements are simply that a reasonably good contact be' had between the treating solution and the hydrocarbon oil for a period of time necessary to effect the desired sweetening and removal or conversion of the mercaptans and means should be provided in the apparatus employed for permitting the settling of the mixture and the drawing off of the spent or partially spent treating agent. For the purposes of this invention I may use conventional petroleum agitator vessels, conventional systems of orifice contact and settling drums, such as are used in sodium plumbite sweetening by'a continuous method, countercurrent packed towers, mechanical stirring chambers, air blowing chambers, other means for discharging oil into a body of the treating agent, or any of the known means in conventional use for contacting immiscible liquids followed by settling trifugal force.

While particular embodiments of this invention are shown above, it will be understood, of course, that the invention is not to be limited thereto, since many modifications may be made, and it is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention.

I claim: 7

1. A process of refining a "hydrocarbon oil which comprises contacting said oil with an alkali metal hydroxide solution having dissolved therein an alkali 'metal salt of'athio acid of phosphorus. 7 K

2. A process of refining a hydrocarbon oil which comprises contacting said oil withan aqueous solution of an alkali metal hydroxide having dissolved therein an alkali 'metal salt of a thioph'osphOricaid.

3. A process of refining a low b'oiling'hydroby gravity or cencarbon oil which comprises contacting said-oil with an aqueous solution ofanalkali'metal hydroxide having dissolved therein at least one-half of one percent by weight of an alkali metal salt of a thiophosphoric acid.

4. A process of refining a low boiling hydrocarbon oil which comprises contacting said oil with an aqueous solution of the reaction product of phosphorous pentasulfide and an aqueous solution of an alkali metal hydroxide.

5. A process of refining a low boiling hydrocarbon oil which comprises contacting said oil with an aqueous solution of an alkali metal hydroxide having a tertiary alkali metal dithiophosphate dissolved therein.

6. A process of refining a low boiling hydrocarbon oil which comprises contacting said oil with an aqueous solution of an alkali metal hydroxide having a. tertiary alkali metal trithiophosphate dissolved therein.

7. A process of refining a hydrocarbon oil of the gasoline boiling range which comprises contacting said oil in the liquid phase with an alkali metal hydroxide solution having dissolved therein an alkali metal salt of a thio acid of phosphorus.

8. A process of refining a hydrocarbon oil of the gasoline boiling range which comprises contacting less than about 100 parts of said oil in the liquid phase with one part of an aqueous solution of an alkali metal hydroxide having dissolved therein at least one-half of one percent by weight of a reaction product of phosphorous pentasulfide and an aqueous solution of an alkali metal hydroxide.

9. The process recited in claim 8 wherein the hydrocarbon oil to be treated is a cracked distillate containing mercaptans.

10. In the process of refining a low boiling hydrocarbon oil, the step of contacting the oil in the liquid phase with an aqueous alkali metal hydroxide solution having dissolved therein an alkali metal salt of a thiophosphoric acid.

11. In the process of refining a low boiling hydrocarbon oil of the gasoline boiling range to remove mercaptan sulfur therefrom, the step of contacting the oil in the liquid phase for a period of one-half minute to 20 minutes with an aqueous alkali metal hydroxide solution having dissolved therein at least one-half of one percent by weight of the reaction product of phosphorous pentasulfide and an aqueous solution of the alkali metal hydroxide.

12. A process of refining a hydrocarbon oil which comprises contacting said oil with an aqueous alkali metal hydroxide solution of an alkali metal salt formed by the reaction of phosphorous pentasulfide With an alkali metal hydroxide.

13. A process of refining a hydrocarbon oil which comprises contacting said oil with an aqueous alkali metal hydroxide solution of the alkali metal salt formed by the reaction of phosphorous pentasulfide with said aqueous solution.

CARL WILLIAM BERGER. 

